1. Field of the Invention
The present invention relates to a specific sulfonyl compound and the use of said compound, and more particularly, in case said compound coexists with a specific developer for thermalsensitive recording medium, an aqueous slurry of developer has a good stability against hydration with lapse of time and the sensitive recording medium is high sensitive, less surface blushing and has the storage stability of recorded image, more particularly excellent in moisture resistance, heat resistance and anti-plasticizer.
2. Prior Art
A thermosensible recording medium has been well known in the art, which uses the thermal-coloring reaction of an electron-donative basic dye precursor and an electron-acceptive developer. Among others, 2,2-bis(4-hydroxy-phenyl) propane and 4-hydroxy-4'-isoproxy-diphenylsulfone are well known as the developer(For example, Japanese Patent KOKOKU No.3-54655, etc.).
However, regarding a thermosensible recording medium to which said developer is applied, further improvements of the storage stability for color development, in particular, the moisture resistance, the heat, resistance and anti-plasticizer have been required. In order to solve these problems, the present inventors previously found a compound having the following formula (2): ##STR2## wherein X represents hydrogen atom or an alkyl group o f1.about.4 carbon atoms; R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are identical with one another or different prom one another, and each of them represents hydrogen atom, a halogen atom or an alkyl group of 1.about.4 carbon atoms, and filed a patent application [Kokai Koho(Publication)No.JP-A-8-247319] on said compound. However, thereafter it was found that a thermalsensitive recording medium to which said compound is applied as a developer is excellent in the above subject matter, however, when an aqueous slurry of said developer was conserved at 40.degree. C., a deterioration of dispersion due to hydration occurs, and then, the thermalsensitive recording medium to which said compound was applied causes a surface-blushing of the supporting base at 6or which should be improved.